Derivative Instruments Level 4 Credit Risk Assumed through Credit Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 39,944		$ 41,099
Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	961		961
Credit Risk Derivatives, at Fair Value, Net	94		92
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	462		503
Credit Risk Derivatives, at Fair Value, Net	8		11
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount			45
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	40
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	43		43
Derivative, Fair Value, Amount Offset Against Collateral, Net	0		0
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	225		225
Derivative, Fair Value, Amount Offset Against Collateral, Net	(1)		(1)
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	22
Derivative, Fair Value, Amount Offset Against Collateral, Net	0
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount			22
Derivative, Fair Value, Amount Offset Against Collateral, Net			(2)
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	0		0
Derivative, Fair Value, Amount Offset Against Collateral, Net	0		0
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	55		57
Derivative, Fair Value, Amount Offset Against Collateral, Net	8		13
Credit Derivatives in Offsetting Positions [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	77		111
Derivative, Fair Value, Amount Offset Against Collateral, Net	1		1
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net			0
Credit Derivatives in Offsetting Positions [Member] | Single Name Credit Default Swaps [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Fair Value, Amount Offset Against Collateral, Net	0
Embedded Derivative Financial Instruments [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount			100
Credit Risk Derivatives, at Fair Value, Net	100		100
Embedded Derivative Financial Instruments [Member] | Other Credit Derivatives [Member] | Debt Securities Payable [Member] | Standard & Poor's, A+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	100
Basket Credit Default Swaps [Member]
Credit Derivatives [Line Items]
Amount of Standard Market Indices of Diversified Portfolios of Corporate Issuers	2,300		1,800
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, BBB+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	475		493
Credit Risk Derivatives, at Fair Value, Net	$ 1		$ 5
Average Term of Credit Risk Derivatives	3 years		3 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 22
Credit Risk Derivatives, at Fair Value, Net	$ 2
Average Term of Credit Risk Derivatives	4 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, B Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount			$ 22
Credit Risk Derivatives, at Fair Value, Net			$ 2
Average Term of Credit Risk Derivatives			4 years
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, CCC Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 55		$ 57
Credit Risk Derivatives, at Fair Value, Net	(9)		$ (13)
Average Term of Credit Risk Derivatives			1 year
Basket Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Collateralized Mortgage Backed Securities [Member] | Standard & Poor's, AA+ Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	124		$ 158
Credit Risk Derivatives, at Fair Value, Net	$ (2)		$ (2)
Average Term of Credit Risk Derivatives	3 years		2 years
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount			$ 88
Credit Risk Derivatives, at Fair Value, Net			$ 0
Average Term of Credit Risk Derivatives			3 years
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, A Rating [Member] | External Credit Rating, Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 142
Credit Risk Derivatives, at Fair Value, Net	$ 2
Average Term of Credit Risk Derivatives	4 years
Single Name Credit Default Swaps [Member] | Credit Default Swap, Selling Protection [Member] | Debt Securities Payable [Member] | Standard & Poor's, CCC+ Rating [Member] | External Credit Rating, Non Investment Grade [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	$ 43		$ 43
Credit Risk Derivatives, at Fair Value, Net	$ 0		$ 0
Average Term of Credit Risk Derivatives	1 year		1 year
Not Designated as Hedging Instrument [Member]
Credit Derivatives [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (48)	$ (3)
Derivative, Notional Amount	38,049		$ 39,141
Not Designated as Hedging Instrument [Member] | Credit Default Swap, Selling Protection [Member]
Credit Derivatives [Line Items]
Derivative, Gain (Loss) on Derivative, Net	8	(2)
Not Designated as Hedging Instrument [Member] | Other Credit Derivatives [Member]
Credit Derivatives [Line Items]
Derivative, Gain (Loss) on Derivative, Net	5	16
Not Designated as Hedging Instrument [Member] | Foreign Exchange Forward [Member]
Credit Derivatives [Line Items]
Derivative, Gain (Loss) on Derivative, Net	17	34
Not Designated as Hedging Instrument [Member] | Credit Derivatives in Offsetting Positions [Member]
Credit Derivatives [Line Items]
Derivative, Notional Amount	925		$ 1,006
Not Designated as Hedging Instrument [Member] | Currency Swap [Member] | Foreign Exchange Forward [Member]
Credit Derivatives [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (4)	$ (2)